import com.sun.org.apache.xerces.internal.xinclude.MultipleScopeNamespaceSupport;

import java.util.Arrays;

public class PriorityQueue {
    public int[] elem;
    public int usedSize;

    public PriorityQueue() {
        elem = new int[10];
    }

    /**
     * 建堆的时间复杂度：
     *
     * @param array
     */
    public void createHeap(int[] array) {
        for(int i = 0;i<array.length;i++) {
            elem[i] = array[i];
            usedSize++;
        }

        for(int i = (elem.length - 1 - 1)/2;i>=0;i--) {
            //向上调整建堆
            shiftUp(i);
        }
    }

    /**
     *
     * @param root 是每棵子树的根节点的下标
     * @param len  是每棵子树调整结束的结束条件
     * 向下调整的时间复杂度：O(logn)
     */
    private void shiftDown(int root,int len) {
        int parent = root;
        int child = parent*2+1;
        while(child<len) {
            if(child+1<len && elem[parent+1]<elem[parent]) {
                child++;
            }
            if(elem[parent]>elem[child]) {
                swap(parent,child);
                parent = child;
                child = parent*2+1;
            }else {
                break;
            }
        }
    }

    private void swap(int a,int b) {
        int tmp=elem[a];
        elem[a] = elem[b];
        elem[b] = tmp;
    }


    /**
     * 入队：仍然要保持是大根堆
     * @param val
     */
    public void push(int val) {
        if(isFull()) {
            elem = Arrays.copyOf(elem,elem.length*2);
        }
        elem[usedSize++] = val;
        shiftUp(usedSize-1);
    }

    private void shiftUp(int child) {
        int parent = (child-1)/2;
        while(parent>=0) {
            if(elem[parent]>elem[child]) {
                swap(parent,child);
                child = parent;
                parent = (child-1)/2;
            }else {
                break;
            }
        }
    }

    public boolean isFull() {
        return usedSize == elem.length;
    }

    /**
     * 出队【删除】：每次删除的都是优先级高的元素
     * 仍然要保持是大根堆
     */
    public void pollHeap() {
        if(isEmpty()) {
            return;
        }
        int ret = elem[0];
        swap(0,usedSize-1);
        shiftDown(0,usedSize-2);
        usedSize--;
    }

    public boolean isEmpty() {
        return usedSize == 0;
    }

    /**
     * 获取堆顶元素
     * @return
     */
    public int peekHeap() {
        if(isEmpty()) {
            return -1;
        }
        return elem[0];
    }
}